Issues and Options for Making Cities Spongy


No life, biotic and abiotic, exist on this planet without water. Despite being most valuable and critical for human living, growth of vegetation, flora-fauna and food; water remains the most misused, abused and in-efficiently used  natural resource.  Around 71 % area of the planet earth remains water covered. Despite, huge amount of water  available and stored in the oceans and the seas, spread across the planet, still  availability of fresh and potable water  eludes majority of the natives of this earth. 96% of sea water being saline, (contains both excessive salt and minerals), makes it unsuitable for human use/consumption. Majority of  potable water available on the earth (occupying 29% area of planet), is locked in the glaciers etc., which remains  inaccessible to the people and communities in the normal course of living and working. In addition, majority of human activities, involving living working, industry  sanitation, are also  primarily water based,  requiring  water on continued basis for remaining operational. Unfortunately, even water supplied for human living remains  most inefficiently used because, out of  total water supplied, only 20% is used/consumed , whereas remaining 80% water goes into drains, as gray and black water. Further in majority of cases, waste water is discharged into fresh/drinking water resources, making such water unfit for human consumption. Accordingly, it is important that water as a resource, is valued , managed and used  both effectively & efficiently.

According to Human Development Report 2006. UNDP, 2006 ; Coping with Water Scarcity Challenge of the twenty-first century. UN-Water, FAO, 2007;

“ Water scarcity is  already affecting every continent. Globally around 1.2 billion people, or almost one-fifth of the world’s population, live in areas of physical scarcity, and 500 million people are approaching this situation. Another 1.6 billion people, or almost one quarter of the world’s population, face economic water shortage (where countries lack the necessary infrastructure to take water from rivers and aquifers). Water scarcity is  emerging as  one of  the major problems to be faced by many societies and the World in the 21st century. Water use has been growing at more than twice the rate of population increase  in the last century. Due to rapid growth in  water consumption, increasing number of regions are facing chronical short of water. Water scarcity is both a natural and a human-led phenomenon. There is enough freshwater on the planet for seven billion people but it is distributed unevenly and  majority of available water is wasted, polluted and unsustainably managed.

Population clock is ticking very fast. As per the latest count, world population has already reached 7.95 billion ( May 29, 2022) .Based on the estimates made, global population is likely to be in the range of 10-12 billion by the year 2050, making it humanly impossible   to  meet the requirement of water of the entire population on this planet earth. Besides meeting the requirements of the human beings, water will also be required to feed large animal stock existing on this planet. Accordingly, search for new options to conserve, preserve and source water for the  future generations of human beings and animal population would remain most challenging and critical.

Looking at the entire context, if majority of cities globally, on one hand. are facing a dilemma  of having acute shortage of drinking water but on the other side, large number of cities also remain in crisis while facing the greatest challenge/threat  from  sudden/repeated  flooding, due to rapid climate change and  natural/  manmade hazards. These floods  make cities  lose vital human resource besides loss of property and infrastructure. In the process, storm water creates  havoc/crisis and make cities and communities suffer physically, socially and economically. These prevailing dualities and contradictions in the urban areas , caused  by  excessive/deficient water, need  appropriate solutions to make sure, water is not only managed rationally when there are floods, but also preserved, effectively and efficiently, to be used during the  lean period of water shortage and crisis.

Water is never static  and remains always on the move. Thanks to water cycle, planet’s water  is constantly moving from one place to another and from one form to another. In this era of unpredictable weather, rapid climate change, shifting pattern of rain,  increasing heat island , global warming , rising urban temperature , human settlements in general and cities in particular are required to  be made safe against these natural disasters and  damage caused by increased flooding. In this era of  increasing environment and climate uncertainties, urgent and innovative solutions are needed to make cities safe and resilient in the event of flooding etc. besides making cities water resilient and sustainable.

Spongy Cities

Globally   cities are  on  the move. They are always  evolving, devolving, never static and never finite. Accordingly, cities are being viewed, reviewed , redefined and renamed  periodically, based on the changing needs of communities; objectives defined and pattern of planning; shape and size of the city;   preserving, protecting and  promoting resources, environment and ecology; making cities people, gender  and technology centric  etc. Cities in the past have accordingly been  named  as; planned cities, garden cities, linear cities, industrial cities, regenerative cities , eco-friendly cities, sustainable cities, inclusive cities, child/women/elders friendly cities, resilient cities, smart cities etc. Considering the fact that cities are  fast emerging as major consumers of energy and resources; generators of  waste and  responsible for generating large carbon footprints, future typologies of cities now include; carbon neutral cities; energy efficient cities; zero water ; zero waste cities etc. In addition, majority of cities are also fast becoming hotbeds of disasters, both manmade and natural, accordingly safe cities is emerging another typology for urban settlements to make them disaster free. Looking at the context of cities getting flooded  periodically due to heavy rains, breach of water channels, rivers, dams etc., leading to enormous loss to humans, social fabric, resources, environment, ecology, economy etc., Sponge city is the terminology  now being deployed for  cities,  to make them safe against floods.

In the parlance of planning,  Sponge city is defined, ‘As an urban area; which has been planned, designed   and constructed  to  effectively and efficiently manage and  cope with the challenges posed by  excessive water/storm water caused by heavy  rainfall, high tides , swollen rivers or other manmade/ natural activities, using a variety of techniques. Sponge city, has also been defined as, ‘the city that is designed to retain, clean, and reuse stormwater.  Basically, sponge city  in its approach,  intent, content, planning, designing , construction and management, has focus on water and its effective and efficient management, without adversely impacting the operation and function of the city, which is subjected to challenge posed by excessive water. Sponge city model promotes, retaining the  excess water within the city aquifer by creating options  to eliminate concrete pavements that separate water from the natural ecosystem; utilize natural wetlands to absorb water into the soil; make city  water-resilient and  transform cities/communities/ neighbourhoods  by helping in redefining  urban landscape  by working across different disciplines — hydrology, landscape, architecture, planning and engineering, to save human lives and property from the threat  posed and damage caused by excess  water.

Sponge city model, as an option and strategy, has been gaining currency and finding favour, both at local and global level  with planners, developers and administrators,  to check , balance   and counter  the threat posed by storm water, emerging out of high intensity of rain causing flooding  in the urban settlements.

Sponge city approach  is primarily visioned to empower , mitigate or prevent flooding of cities by providing sufficient  options  in terms of creating urban spaces , creating water bodies, promoting porous parking, investing in rainwater harvesting and  ground water recharging , to create   appropriate level of ability/capacity  to naturally absorb large amount of surplus water without flooding the city. 

Sponge City portrays a particular typology, which makes city porous  to  acts like a sponge and  absorbs the surplus/rain water, which is then naturally filtered by the soil and allowed to reach into the urban aquifers to  be easily sourced and used for meeting the needs of  the city. In fact, sponge city, as a concept,  believes in retaining the surplus water rather than  draining water. It serves dual purpose for a city. Besides saving city from flooding, it retains the precious water for meeting the basic and essential needs of the city. In-fact Sponge cities will never ever have the opportunity to run for water with cities facing water shortage for its citizens and communities to meet their daily needs. Sponge Cities  are also known for their capacity, capability and advantage to combat  and meet  effectively the challenges posed by climate change, global warming and make cities more livable, sustainable, safe, resilient and inclusive.

Why Build Spongy Cities.

World is urbanizing rapidly with more than 55% population living in cities. Under the pressure of rapid urbanization, new cities are mushrooming and old cities are expanding in size and contents . Cities are developing too fast, with majority of open spaces getting converted/covered by buildings, roads, parking, pavements and hard surfaces, leaving minimum  open/ porous areas  for water to percolate. Cities remain largely depending upon ground water to meet basic requirement of human living This invariably leads to depletion of ground water at faster pace. Majority of the cities are becoming water deficient due to low availability of ground water and are looking at the different options to source water from distant resources for meeting the water based needs of the people/communities. This calls for creating effective mechanism to replenish the fast depleting ground water and making sufficient water available for  the use of communities/cities locally.

Unfortunately, water made available by the natural water cycle/rains is not being sourced /tapped  effectively and is made to run fast on the roads/streets ,  causing flood and making water accumulate in low -lying areas, causing enormous destruction/damage to human living  and property. Thus, communities and cities  remain the greatest loser in terms of not only wasting precious water but also suffering enormous damage due to inability to manage/tap the  valuable water, effectively and efficiently. In the process cities are also becoming unsafe to live and work. The existing malady  of cities becoming unsafe can be  largely attributed to the way cities are being planned, designed and developed. Prioritizing vehicle based mobility; planning for vehicles; commercialization of urban land; minimization of open spaces using low-lying areas for urbanization; eliminating all existing water channels, destroying existing flora , fauna and bio-diversity; paving all available open spaces etc. are  few reasons to  make cities unsafe due to excessive storm water. Focus of the city managers remains to collect and  drain all the precious  storm water through a network of drainage system outside the city, losing the precious water resource, which otherwise would have been used for meeting the daily needs of the people and the communities.

Considering the emerging scenario of rapid increase in human and animal population;  ever increasing demand of  potable water; non-availability of adequate ground /potable water; ever rising pollution of water resources; rising temperature, climate change and global warming  etc., cities will have to be planned, designed and developed, differently and distinctly, to remain focused, in order to retain/ source all the water which becomes available to the city in different forms ,from time to time. Planning with  focus on water will help in not only making cities water resilient but also save them from the impending danger of getting damaged due to floods etc. Making cities spongy offers the best option to make cities carbon neutral, minimize heat island and achieve the defined objectives of safety, security, sustainability,  livability and water resilience.

Options to Make Cities Spongy

Studies made and analysis carried out globally have revealed that  due to rapid climate change, global warming and unplanned growth and development, cities  are  increasingly  becoming unsafe and unsustainable , facing the threat  posed by   heavy  precipitation rainfall, and flooding. Accordingly, cities need to be made safe and secure against all manmade and natural disasters. Spongy cities, as a planning typology, is fast emerging as a preferred option to secure the cities against majority of challenges facing the cities. Options for planning and making cities Spongy, should invariably  involve and revolve around;

  • Adopting a Regional approach to water management by integrating the urban water system with rural setting/agriculture- making urban water system integral part of rural water eco-system.
  • Making water and its management, as integral part of urban/ local area planning and designing process including preparing Master plans/Development Plans/Zonal Plans.
  • Providing options for creating large open spaces within cities , for maximizing water retention, and minimizing carbon footprints.
  • Minimizing the extent, area and number of hard surfaces and increasing the amount of absorbent land in the cities.
  • Supplementing and supporting open spaces with efficient channeling system and creating sufficient storage systems within the city
  • Using traditional wisdom and skill for collecting , storing and managing water.
  • Adopting nature based options/infrastructure to promote ground water recharging and retaining surplus water for use of the community.
  • Adopting distinct pattern of landscaping which can help promote porosity in the area, and make value addition to the nature and surrounding environment.
  • Revitalizing derelict wetland by transforming the area into landscaped zone, for addressing urban flooding problems and increasing biodiversity.
  • Creating extensive Green( Vegetation) and Blue (water) network, as integral and essential part of city planning process.
  • Promoting/incentivizing rooftop green spaces and promoting Green walls/green surfaces within/outside building to increase porosity of the built environment.
  • Promoting ground water recharging, water storage and rain water harvesting at local /community/city/peri-urban areas on large scale.
  • Reviving/ Restoring/maintaining all existing water channels in the urban setting.
  • Making roads/parking porous- using porous materials/ concrete.
  • Finding space/creating options for storage of rain water- below road crossing/inter-sections.
  • Promoting urban landscaping and planting trees with large water absorbing capacity.
  • Promoting concept of urban forestry on large scale, to increase porosity of city.
  • Redefining planning norms and building bye-laws to minimize building footprints and increase the porous area within the plotted development.
  • Making provision for creating additional green areas within the built space to compensate the area covered by the building at ground level.
  • Prescribing norms and standards for trees to be planted in the areas under institutions/industry/parking etc.


Essentials for Sponge City

A sponge  city needs to have abundance of porous spaces that allow water to seep through. For  becoming Spongy , cities would need to focus on (World Future Council);:

  • Creating Contiguous open green spaces; Creating/promoting interconnected green belts, waterways, channels and ponds across neighborhoods that can effectively retain and filter water as well as foster urban ecosystems, boost bio-diversity and create cultural and recreational opportunities on the pattern followed in the planning of Chandigarh and its neighbourhood units( Sectors).
  • Promoting Green roofs and Green walls; Using  innovatively   available space on the top of buildings which remains most unused/abused and large area of building envelop; for creating porous green space for  retaining rainwater, naturally filtering it before it is recycled or released into the ground.
  • Adopting Porous designinterventions across the city, including construction of bio-swales and bio-retention systems to detain run-off and allow for groundwater infiltration; porous roads and pavements that can safely accommodate car and pedestrian traffic while allowing water to be absorbed, permeate and recharge groundwater; drainage systems that allow trickling of water into the ground or that direct storm water run-off into green spaces for natural absorption
  • Promoting Water savings and recycling,including extending water recycling particularly of grey water at the building block level, incentivizing consumers to save water through increased tariffs for increase in consumption, raising awareness campaigns, and improved smart monitoring systems to identify leakages and inefficient use of water.
  • Educating stakeholders and involving communities; by engaging CBOs, NGOs for making local communities/people aware about the distinct advantages  Spongy City holds-and making spongy city,  a people/ community led- programme.
  • Prescribing realistic and rational norms and standards for open spaces in the urban planning and development process. Green space, are known for their capacity to hold and absorb lot of water and can accordingly  make a significant difference in reducing the severity and frequency of flooding events, when provided rationally.
  • Allocating adequate resources/funds; in the urban development for the implementation of innovative water management strategies that would gradually transform   and make cities Spongy
  • Involving elected representatives ,both at community/local/state level, for sourcing  support to make cities Spongy.
  • Retrofitting/reclaiming; derelict sites, existing industrial structure, abandoned landfills  and wetlands  and converting them  into  Parks/green spaces for promoting recreation, environment, porosity and creating  innovative  options for water management ecosystem.
  • Using nature based options/infrastructure; to promote ground water charging and retaining surplus water for use of the community. Nature based sponge city infrastructure are known to  performs the same function as traditional infrastructure, which  aims at drainage and re-use only, whereas a natural system provides many additional environmental and socio-economic benefits.
  • Undertaking a detailed land suitability analysis; of the cities/land to be used for urbanization; identifying all  existing low lying area  and  using them for creating water bodies/ storing water/ open spaces/ponds and lakes, which can hold  the excess water.

Issues/ challenges  in making cities Spongy

In this ongoing era of massive urbanization; uncontrolled and unregulated migration; rapidly increasing land values; high degree of land speculation;  increasing culture of uncontrolled, unregulated, unplanned and haphazard growth and development; making cities spongy remains both a difficult and a challenging task. As per World Future Council, major challenges facing the creation of Sponge City involve;

  • Availability of less porous area in the Cities;
     Uncontrolled urbanization and urban sprawl have led to creation of  large proportion of  impermeable areas comprising of impervious roads, pavements, roofs and areas under parking which do not allow water to be absorbed into the ground. Such  impervious surfaces collect the rainwater through the urban drainage infrastructure and channel it into rivers, lakes or into the sea. This traditional type of design led to the creation of cities which are increasingly becoming impermeable and have adverse impact on the natural water cycle.
  • Focus on Drainage Water and not on Retaining water
    Focus of the existing  water systems in the urban area, remains on the  speedy collection and drainage of waste/storm water  from the city within minimum timeframe. There exists no system of water management in the urban water supply chain with the result rain water and wastewater , including water from our sinks and toilets, is collected by one single drainage system; drainage system/network created within the city, collects all the rain water and the wastewater  and directs it to a wastewater treatment plant where it gets treated before it is discharged into rivers /nearby water bodies. When it rains excessively, wastewater treatment plant cannot accommodate all the water that the drainage systems carry. Accordingly, much of the  rain water , mixed with the untreated wastewater is discharged into rivers. The more impermeable the city is, the more  rain water will be mixed with wastewater and discharged directly into rivers polluting the local water bodies in the process. In large majority of urban areas in India , even where sewerage system has been installed,  sewerage treatment plants are  conspicuous by their absence. In cities where STPs have been put, they remain inadequate /inefficient to treat the entire waste water leading to aggerating the pollution of water bodies and the environment.


  • Limited availability of green/porous areas
    With urban land becoming highly expensive, focus of the all land developing agencies, including public and private, is  to maximize the benefits from the available land by  putting  large proportion of land under the plotted/commercial development. This trend has led to limiting the availability of green spaces in the urban setting. Even where the provision is made of provide large areas  as non-saleable, majority of such component is used for institutional/infrastructure development. Component of open spaces remains unspecified in the urban legal framework despite the fact norm of 9 sqm per capita of open spaces has been  specified by  the WHO to create open spaces in the urban context. Limiting/minimsing  the proportion of open spaces and rapid/uncontrolled urbanization has led to  large scale degradation of urban ecosystems and green areas due to uncontrolled urban  sprawl, which  inter-alia has  led to; considerable loss of urban biodiversity  and  creating numerous environment related problems in terms of ;  drop in available green areas for natural ground filtration of storm water;  decrease in CO2 capture by plants;  fewer spaces for natural cooling  and generally less livable, healthy, comfortable and attractive public spaces.


  • Increasing intensity and frequency of urban flooding
    With rapid climate change globally, cities are facing numerous challenges  posed by unpredicted increase in the frequency and intensity of  extreme weather events. With reduced  open spaces, water absorbing capacity of the urban areas has undergone enormous reduction, which has led to increase in the danger of  urban flooding. Increased incidences of flooding have invariably led to increased groundwater pollution adversely impacting cities in terms of damaging  properties and  creating health related issues.


Value addition made by Sponge City 

Sponge city, as a concept and approach to urban planning and development, does not represent merely another typology of cities, but offers distinct tangible and intangible  benefits/ advantages to environment, ecology, climate ,  bio-diversity , sustainability, safety of individuals, communities, cities and planet earth by minimizing global warming; reducing carbon-footprints; minimizing urban heat island; connecting cities with nature; making cities safe and climate resilient; improving availability of vital oxygen supply; minimizing air pollution; reducing urban flooding; augmenting the supply of fresh water and making cities better places for human habitation besides improving the quality of urban living; making cities  operationally and economically efficient and lowering the cost of providing urban services.

As per World Future Council, wide range of benefits associated with the implementation of sponge cities would include;

  • Increased supply of clean water; . Sponge City helps in replenishing groundwater and thus  ensures local availability / accessibility to water resources for  the cities. This also entails greater water self-sufficiency which allows cities to increasingly rely on water sources from within  local boundaries
  • Cleaner groundwater;due to the increase volume of naturally filtered storm water. This means lower environmental and health costs due to considerable decrease in water pollution
  • Reduction in flood risk;as the Sponge city offers more permeable spaces for the natural retention and percolation of water. This leads to better resilience and  greater ability on the part of the city  to deal with higher flood risks resulting from climate change
  • Lower burdens on drainage systems, water treatment plant, artificial channels and natural streams due to reduced flow of waste/polluted water, lowering costs for creating/operating/maintaining drainage and treatment infrastructure
  • Greener, healthier, more enjoyable urban spaces; Higher order of greener urban spaces are known to improve quality of life, create more pleasant landscape/ recreational areas that are enjoyable / attract people. This also leads to increase in land value due to aesthetically more pleasing, cleaner and healthier open spaces when created close to private properties
  • Enriched biodiversity; Open/ green spaces, wetlands, parks, green belts and green rooftops are known to create large options for flora and fauna to come back and increase bio-diversity of the city.
  • Making cities Carbon Neutral; Large wealth of greenery and trees helps in creating large capacity for the city to  siphoned off carbon from the environment, reducing considerably the carbon footprints of the cities besides removing particulates from the air.
  • Lowering Urban Heat Island / urban temperature; due to presence of large green area
  • Making Cities more Energy efficient; due to reduced  urban temperature and  lower urban heat island impact.


Rapid rural-urban migration;  ever increasing urban population ;uncontrolled  growth and expansion of cities; changing  dynamics of urban growth and development; high degree of land speculating; trading land as an economic commodity ; grey options replacing green spaces; inadequate/insufficient   urban drainage systems unable to cope with rising flood risk etc.; calls for  evolving, innovating and prioritizing innovating green solutions for making cities  safe and water resilient.

 Sponge City, as a strategy and as an option, focuses on using pervious pavements, open spaces, parks and gardens, green roofs, urban wetlands, and other porous options to absorb water during excessive rains and make city safe against any water related threats and disasters. Green/porous spaces are known for their capacity, capability and distinct advantage to purify/retain water for a longer time and release water gradually  like a sponge.  Studies made and analysis carried out have revealed that, Sponge cities with green features on merely 20% of their land, are known to help in  achieving the goal of retaining/ reusing 80% of annual precipitation.

 Making cities Sponge would also involve  going beyond and using options of creating  merely green features and would need additional support system in terms of ; construction of  adequate capacity of drainage networks, constructing underground stormwater storage tanks, and  creating other flood-control/mitigation facilities, depending upon prevailing conditions  of rainfall/precipitation in the city. These  additional support measures will remain city/area specific. Though prime  objective of the Sponge City project  remains  to protect the city from  the onslaught of floods, but making cities spongy also provides large number of additional/distinct advantages to the city and its numerous stakeholders  in terms of minimizing  severity of the rainfall; eliminating  flood-prone locations ;  reducing flood peaks; promoting sustainable circulation and recovery of rainwater besides  providing  other environmental and ecological advantages.

 China ,as a nation, has invested heavily  to promote the concept and ideology of making cities Spongy,  for  making cities safe against floods and resilient for water. The 34 hectares urban storm water park in the city of Harbin in northern China is an example of successful Sponge City intervention. The storm water park provides multiple ecosystems services in terms of ; collecting, cleansing and storing storm water and letting it infiltrate it into the aquifer; protecting and recovering the native natural habitats;  providing an aesthetically appealing public space for recreational use; putting in place  water-intensive plants and trees and creating land basins to hold excess water.

Sponge cities, as a  concept and approach,  remain relevant  and can have  much-needed impact in promoting the rational development of urban settlements in the  developing countries, especially in India and  in southeast Asia, where flooding is more frequent  because of seasonal heavy rain and the prevailing region’s tropical climate. Sponge city model  besides helping in providing affordable solution to  prevailing/impending global water crisis, will also go a long way  in redefining our relationship with nature to make development and nature mutually supportive, removing all  prevailing mismatch, dualities and contradiction existing between them. Spongy city concept can also be innovatively and effectively utilized by planners in Smart Cities to achieve the agenda defined in the SDG 11, to make cities and communities safe, resilient, inclusive and sustainable.

Note ;All images  used in the paper  to illustrate the text has been sourced from the platform of Google, which are  thankfully  and gratefully acknowledged.



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